ECLSS was an agency or title held by a Starfleet officer at Starfleet Command's Fleet Operations Center, Sol Sector.
In January of 2155, Starfleet officers B. Blackman, M. Moore, J. Pizston, and J. Wischnack was working in or as ECLSS. It and the officers' name were listed on directory placards. (ENT: "Demons", directories)